JP6794718B2 - Electrodeposition liquid for forming water-dispersed insulating film - Google Patents

Description

The present invention relates to an electrodeposition liquid for forming an aqueous dispersion type insulating film, which is used when forming an insulating film provided by an insulating material such as an insulated electric wire by an electrodeposition method.

Conventionally, an insulating material such as an insulated electric wire whose surface is covered with an insulating film has been used for a motor, a reactor, a transformer and the like. As a method of forming an insulating film on the surface of an electric wire, a dipping method, an electrodeposition method (electrodeposition coating), and the like are known. The dipping method is a method of forming an insulating film having a desired film thickness by repeating a step of using, for example, a flat wire as an object to be coated, dipping it in a paint, pulling it up, and then drying it. .. On the other hand, in the electrodeposition method, electrically charged paint particles are deposited on the object to be coated by passing a direct current through the object to be coated immersed in the electrodeposition paint (electrodeposition liquid) and the electrodes inserted in the electrodeposition paint. This is a method of forming an insulating film.

The electrodeposition method is attracting attention because it is easier to apply with a uniform film thickness than other methods, and it is possible to form an insulating film with high rust prevention and adhesion after baking. Improvements have been made. For example, as a coating material used in an electrodeposition method, particles of a block copolymer polyimide having a siloxane bond in the molecular skeleton and an anionic group in the molecule and having a predetermined average particle size and particle size distribution. A suspension-type polyimide electrodeposition coating material is disclosed (see, for example, Patent Document 1). It is said that this electrodeposition coating material has excellent storage stability that does not easily deteriorate even after long-term storage, and can form an electrodeposition coating film having high uniformity in film properties at a high electrodeposition rate.

Further, as an electrodeposition material used in the electrodeposition method, an electrodeposition material containing a polyamide-imide-based material as a main component and introducing polydimethylsiloxane into the molecular chain of the polyamide-imide-based material is disclosed ( For example, see Patent Document 2.). In this electrodeposition material, by using a polyamide-imide-based material having a predetermined molecular structure, it is possible to impart heat resistance particularly required for coating sliding members and the like, and cracks in the electrodeposition coating film. Etc. are said to be able to be suppressed.

In the above-mentioned conventional patent document 1, since polyimide particles having an anionic group in the molecule are used, the surface potential of the particles is large, and the dispersibility is improved by the electrostatic repulsive force between the particles. Therefore, even if the electrodeposited liquid after preparation is stored for several days, the occurrence of particle aggregation or sedimentation is suppressed. However, since it is necessary to use a diamine having a carboxyl group or a sulfonic acid group, or a tetracarboxylic acid anhydride having a carboxyl group or a sulfonic acid group that does not contribute to the imide bond, the types of monomers that can be used are limited. Therefore, the manufacturing cost becomes high. Further, in the above-mentioned conventional patent document 2, a water-soluble polyamide-imide is used as a resin, and a water-insoluble continuous film is formed on the conductor surface during electrodeposition. Therefore, if the formation of the film progresses to some extent, the subsequent electrodeposition efficiency deteriorates, and there is a problem that it becomes difficult to form an insulating film having a desired thickness.

With respect to the problems of the prior art, the present inventors have developed a new electrodeposition solution having excellent dispersion stability while using polymer particles having no anionic group in the main chain. Engaged in. Polymer particles that do not have anionic groups have a small surface potential because they do not have anionic groups, and the electrostatic repulsive force between the particles is small, so that the dispersibility in the electrodeposited liquid deteriorates and the particles aggregate. Or there is a concern that it will easily settle. With respect to such problems, in the newly developed electrodeposition solution, good dispersibility of the polymer particles in the electrodeposition solution is ensured by controlling the average particle size and particle size distribution of the polymer particles under predetermined conditions. As a result, the occurrence of aggregation or sedimentation of polymer particles is suppressed even after storage for several days.

Japanese Patent No. 5555063 JP-A-2002-20893

On the other hand, in developing the electrodeposition solution, a new problem has emerged regarding the storage stability of the electrodeposition solution, which is different from the above-mentioned problem of aggregation or sedimentation of polymer particles. For example, if an electrodeposition solution stored for several days is used and the amount of the electrodeposition solution applied is increased in order to form a relatively thick insulating film, the viscosity of the electrodeposition solution increases during storage. As a result, it was found that foaming is likely to occur when the coating film is dried or fired. For this reason, there has been a problem that it becomes difficult to form an insulating film having a desired thickness by using the electrodeposited liquid after storage. Therefore, there has been a demand for early development of an electrodeposition solution that can overcome these new problems related to storage stability.

An object of the present invention is an aqueous dispersion type insulating film having excellent storage stability, suppressing an increase in viscosity of an electrodeposited liquid even after long-term storage, and suppressing foaming during drying or firing of a coating film. The purpose is to provide an electrodeposition liquid for forming.

As a result of further diligent research on the above-mentioned new problems related to storage stability, the present inventors have conducted a compound having specific properties in components other than polymer particles, which are usually contained in an electrodeposition solution. We have developed an electrodeposition solution that can solve these problems by selectively using.

The first aspect of the present invention is a polyamide-imide in which the polymer particles do not have an anionic group in the main chain in an electrodeposition solution for forming an aqueous dispersion type insulating film containing polymer particles, an organic solvent, a basic compound and water. The basic compound is a nitrogen-containing compound having an HSP distance of 36.2 to 43.0 from water, and the volume-based median diameter (D ₅₀ ) of the polymer particles is 0.112 to 0.175 μm . Moreover , the number of particles within ± 30% of the particle size of the polymer diameter (D ₅₀ ) is 54 to 67% (volume basis ) of the total particles.

The electrodeposition solution for forming an aqueous dispersion type insulating film according to the first aspect of the present invention contains polymer particles, an organic solvent, a basic compound and water, and the polymer particles do not have an anionic group in the main chain. The basic compound is a nitrogen-containing compound having an HSP distance of 36.2 to 43.0 from water, and the volume-based median diameter (D ₅₀ ) of the polymer particles is 0.112 to 0.175 μm. 54 to 67% (volume basis) of the total particles are present and are within ± 30% of the particle size of the polymer diameter (D ₅₀ ) . As a result, the storage stability of the electrodeposited liquid is improved, the increase in viscosity of the electrodeposited liquid can be suppressed even after long-term storage, and foaming can be suppressed during drying or firing of the coating film.

Further, in the electrodeposition solution for forming an aqueous dispersion type insulating film according to the first aspect of the present invention, since the basic compound is an alkylamine compound, the effect of improving the storage stability of the above-mentioned electrodeposition solution is further enhanced. Be done.

It is a figure which represented typically the electrodeposition coating apparatus of embodiment of this invention.

Next, a mode for carrying out the present invention will be described with reference to the drawings. The electrodeposition solution for forming an aqueous dispersion type insulating film contains polymer particles, an organic solvent, a basic compound and water. A poor solvent may be contained in addition to water.

<Polymer particles>
The polymer particles contained in this electrodeposition liquid are composed of polyamide-imide, which is a polymer. The reason why the particles made of polyamide-imide are used as the polymer particles is that they are superior in heat resistance and flexibility as compared with other polymer particles.

The average particle size of the polymer particles is not particularly limited from the viewpoint of suppressing foaming during drying or firing, and those having a particle size used for general electrodeposition liquid applications can be used. For example, polymer particles having an average particle size preferably in the range of 0.05 to 1.0 μm can be used. The average particle size of the polymer particles referred to here refers to the volume-based median diameter (D ₅₀ ) measured by a dynamic light scattering type particle size distribution measuring device (model name: LB-550 manufactured by HORIBA, Ltd.). ..

As for the polyamide-imide constituting the polymer particles, the polyamide-imide or the like used for general electrodeposition liquid applications can be used as the resin constituting the polymer particles. For example, it may be a polyamide-imide having an anionic group in the main chain or a polyamide-imide having no anionic group in the main chain. The anionic group, as such -COOH group (carboxyl group) or -SO ₃ H (sulfonic acid group), in a basic solution such as proton is eliminated -COO ^- nature take on negative charge of such group Refers to a functional group having. When polymer particles composed of polyamide-imide having an anionic group in the main chain are used, a large electrostatic repulsive force can be obtained between the particles due to the high surface potential of the polymer particles, and the dispersibility in the electrodeposition liquid can be improved. It is improved and the aggregation or sedimentation of polymer particles is suppressed even after storage for several days.

Therefore, the polyamide-imide constituting the polymer particles preferably has an anionic group in the main chain in order to suppress aggregation or precipitation of the polymer particles, but particularly has an anionic group from the viewpoint of suppressing foaming. Not limited to things. In addition, for those having an anionic group in the main chain, it is necessary to use a monomer having an anionic group as the monomer used for the synthesis, and the monomers that can be used are limited, so that the manufacturing cost increases. There is. Therefore, in order to reduce the cost, it is desirable to use polymer particles composed of polyamide-imide having no anionic group in the main chain.

On the other hand, the polymer particles composed of polyamide-imide having no anionic group in the main chain show a value having a relatively small surface potential. Therefore, the dispersibility due to the electrostatic repulsive force between the particles may not be sufficiently obtained, but it is possible to improve the dispersibility by controlling the particle size and the particle size distribution. Therefore, in order to further reduce costs and suppress aggregation or sedimentation in addition to suppressing foaming, it is desirable to more strictly control the particle size and particle size distribution of the polymer particles in consideration of dispersibility. When polymer particles having no anionic group in the main chain are used, the volume- based median diameter (D ₅₀ ) is 0.05 to 0.5 μm, and the particle diameter of the median diameter (D ₅₀ ) is ±. It is preferable that the number of particles within 30% is 50% or more ( volume basis) of all particles. That is, the polymer particles show a median diameter (D ₅₀ ) in the range of 0.05 to 0.5 μm when the volume- based particle size distribution of the powder composed of the particles is measured, and the particle size distribution is the same. 50% or more of particles having a particle element is distributed within a range of ± 30% of the median diameter _{(D 50) ([D 50} -0.3D 50] μm~ [D 50 + 0.3D 50] within the range of [mu] m) It is something to do. The proportion of particles ( volume basis) distributed within ± 30% of the volume- based median diameter (D ₅₀ ) and median diameter (D ₅₀ ) is determined by the laser diffraction scattering type particle size distribution measuring device (HORIBA). It is based on the volume- based particle size distribution measured by Model Name: LA-960) manufactured by HORIBA, Ltd. Further, the polyamide-imide having no anionic group in the main chain means at least a polyamide-imide having no anionic group in a carbon atom other than the terminal of the main chain. The reason why the volume- based median diameter (D ₅₀ ) of the polymer particles having no anionic group in the main chain is preferably in the above range is that if the volume- based median diameter (D ₅₀ ) becomes too small, it will be described later. This is because the polymer particles form a continuous film during electrodeposition when forming the insulating layer of the above, and the electrodeposition efficiency is gradually lowered, which may make it difficult to thicken the insulating layer. Further, by controlling the volume- based median diameter (D ₅₀ ), even if the formation of the insulating layer progresses to some extent due to electrodeposition, it is possible to easily maintain a good current flow thereafter. The reason is that the conductive water contained in the solvent tends to exist between the polymer particles. On the other hand, if the volume- based median diameter (D ₅₀ ) becomes too large, precipitation may occur in the electrodeposited liquid stored for several days. The reason why the proportion of particles distributed within ± 30% of the volume- based median diameter (D ₅₀ ) is preferably 50% or more is that even if the proportion of the particles becomes too small, it is stored for several days. This is because precipitation may occur in the electrodeposited liquid. Of these, the polymer particles having no anionic group have a volume- based median diameter (D ₅₀ ) of 0.08 to 0.25 μm and are distributed within ± 30% of the median diameter (D ₅₀ ). More preferably, the proportion of particles is 75% or more.

The polyamide-imide constituting the polymer particles is a reaction product (resin) obtained by polymerizing a diisocyanate component containing an aromatic diisocyanate component and an acid component containing trimellitic acid anhydride as a monomer. is there.

The diisocyanate components include diphenylmethane-4,4'-diisocyanate (MDI), diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenyl ether-4,4'-diisocyanate, and benzophenone-4,4'. Examples thereof include aromatic diisocyanates such as −diisocyanate and diphenylsulfone-4,4′-diisocyanate.

The acid components include trimellitic dianhydride (TMA), 1,2,5-trimellitic acid (1,2,5-ETM), biphenyltetracarboxylic dianhydride, and benzophenonetetracarboxylic dianhydride. , Diphenylsulfonetetracarboxylic dianhydride, oxydiphthalic dianhydride (OPDA), pyromellitic dianhydride (PMDA), 4,4'-(2,2'-hexafluoroisopropyridene) diphthalic acid dianhydride Such as aromatic acid anhydrides.

A polyamide-imide resin varnish can be obtained by mixing equal amounts of these diisocyanate components and acid components and heating them in an organic solvent to carry out a polymerization reaction. One type of each of the isocyanate component and the acid component may be used, or a plurality of types may be used in combination.

Further, the polyamide-imide constituting the polymer particles preferably does not have a siloxane bond. This is because if a siloxane bond is present, the siloxane bond is easily thermally decomposed, which may cause a problem that the heat resistance of the insulating film is deteriorated. Since the presence or absence of a siloxane bond is due to the use of a monomer containing a siloxane bond, a polymer having no siloxane bond can be obtained by using a monomer that does not contain a siloxane bond.

<Organic solvent, water, poor solvent>
Organic solvents include 1,3-dimethyl-2-imidazolidinone (DMI), N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, tetramethylurea, hexa. Polar solvents such as ethyl phosphate triamide and γ-butylolactum can be used. Further, examples of water include pure water, ultrapure water, ion-exchanged water and the like. When a poor solvent is contained in addition to water, the poor solvent includes aliphatic alcohols such as 1-propanol and isopropyl alcohol, ethylene glycols such as 2-methoxyethanol, 1-methoxy-2-propanol and the like. Propylene glycols and the like can be used.

<Basic compound (dispersant or neutralizer)>
The basic compound is a component added to the electrodeposition liquid as a neutralizing agent or a dispersant, and a nitrogen-containing compound having an HSP distance of 35 or more with water is used as the basic compound. Here, the HSP (Hansen Solubility Parameter) is a value used as an index of solubility indicating how much a substance is soluble in a certain substance. This HSP value is composed of three parameters, a dispersion term (dD), a polarity term (dP), and a hydrogen bond term (dH), and shows a value unique to each substance. Since these three parameters can be regarded as coordinates in the three-dimensional space (Hansen space), the HSP value is represented as a vector whose starting point is 0 in the space and whose ending point is the coordinates given by the HSP value. The HSP distance (Ra) is the distance between the coordinates or the distance between the vectors given by the HSP values of the two substances, and is generally calculated by the following formula (1).

HSP distance = [4 × (dD _{1 −} dD ₂ ) ² + (dP _{1 −} dP ₂ ) ² + (dH _{1 −} dH ₂ ) ² ] ^1/2 (1)

In the above formula (1), dD ₁ , dP ₁ , and dH ₁ are HSP values of one of the two substances, and dD ₂ , dP ₂ , and dH ₂ are HSP values of the other substance. It is shown that the substances having a smaller HSP distance calculated by the formula (1) have higher compatibility between the two substances. For a nitrogen-containing compound having an HSP distance of 35 or more with water, the HSP value of water (dD = 15.5, dP = 16, dH = 42.3) and the HSP value of the nitrogen-containing compound are expressed in the above formula (1). It is a nitrogen-containing compound having a value (HSP distance) of 35 or more calculated by substitution.

By using a nitrogen-containing compound having an HSP distance of a predetermined value or more from water as the basic compound contained in the electrodeposition solution, the storage stability of the electrodeposition solution can be improved. As a result, even if the electrodeposited liquid after preparation is stored for a long period of time, an increase in the viscosity of the electrodeposited liquid can be suppressed, and foaming occurs during drying or firing of the coating film to prevent a decrease in film thickness. The technical reason for improving the storage stability of the electrodeposited liquid by using a nitrogen-containing compound exhibiting such physical property values has not been clarified at present, but for example, the following reasons are the main technical reasons. Inferred as. The basic compound binds to the polymer structure and works to enhance the dispersibility of the electrodeposited liquid. When the basic compound is hydrophilic such as 2-aminoethanol, the water in the electrodeposition solution is easily approached to the polymer particles, so that the polyamide-imide is easily hydrolyzed. When polyamideimide is hydrolyzed, polar groups such as carboxyl groups and amino groups are generated. Therefore, the liquid viscosity increases by attracting polar solvents such as DMI and water, and the polymer takes in the solvent and partially gels. Can be considered. On the other hand, if a basic compound having a large HSP distance to water and a low affinity to water, that is, having high hydrophobicity is used, it is difficult for water to come close to the polymer particles, so that the electrodeposition solution associated with hydrolysis as described above It is thought that changes can be suppressed. The upper limit is not particularly limited as long as the HSP distance to water reaches at least 35, but the HSP distance to water is 35 to 45 due to the relationship with the HSP value of the nitrogen-containing compound that can be confirmed at present. Is preferable.

Specific examples of the nitrogen-containing compound which exhibits such physical property values and is suitable as a basic compound contained in the electrodeposition liquid include an alkylamine compound. Further, examples of the alkylamine compound include primary alkylamines such as propylamine, butylamine, amylamine, hexylamine, octylamine and decylamine, and second alkylamines such as dipropylamine, dibutylamine, diamylamine, dihexylamine and dioctylamine. Examples thereof include tertiary alkylamines such as tertiary alkylamines, tripropylamines, tributylamines, triamylamines and trihexylamines. Of these, tripropylamine, tributylamine, triamylamine, trihexylamine and the like are particularly preferable because they have a large HSP distance from water and exhibit high hydrophobicity.

<Preparation of electrodeposition solution>
The electrodeposition liquid can be obtained, for example, by the following method. First, a polyamide-imide resin varnish is synthesized using a diisocyanate component, an acid component, and an organic solvent as described above. Specifically, the diisocyanate component and the acid component as monomers are prepared respectively, and an organic solvent such as DMI is charged into the flask at a predetermined ratio together with these. As the flask, it is preferable to use a four-necked flask equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe, a thermometer, and the like. The blending ratio of the diisocyanate component and the acid component is preferably a molar ratio of 1: 1. Further, the ratio of the organic solvent is preferably a ratio corresponding to 1 to 3 times the mass of the resin obtained after synthesis. After putting these into the flask, the temperature is preferably raised to a temperature of 80 to 180 ° C., and the reaction is preferably carried out for 2 to 8 hours.

Then, if necessary, by diluting with the above-mentioned organic solvent, a polyamide-imide resin varnish containing a polyamide-imide resin synthesized as a non-volatile component in a proportion of preferably 20 to 50% by mass can be obtained.

In order to prepare an electrodeposition solution for forming an aqueous dispersion type insulating film from the polyamide-imide resin varnish synthesized in this way, the above-prepared polyamide-imide resin varnish is further diluted with the above-mentioned organic solvent, if necessary, and here. The above-mentioned basic compound is added as a dispersant or a neutralizing agent. At this time, a poor solvent may be added if necessary. Then, water is added and sufficiently dispersed at room temperature while stirring preferably at a rotation speed of 8000 to 12000 rpm. When a poor solvent is added, the preferable ratio of each component in the electrodeposition solution is polyamide-imide resin / organic solvent / poor solvent / water / basic compound = 1 to 10% by mass / 60 to 79% by mass / balance. / 10 to 20% by mass / 0.05 to 0.3% by mass.

By the above steps, the above-mentioned electrodeposition liquid for forming an aqueous dispersion type insulating film can be obtained.

<Manufacturing of insulation>
Subsequently, as a method for producing an insulator in which an insulating film is formed on a metal surface using the electrodeposition liquid for forming an aqueous dispersion type insulating film, an example of a method for producing an insulated wire in which an insulating film is formed on the surface of the electric wire is used. Will be described based on the drawings. As shown in FIG. 1, the electrodeposition liquid 11 is electrodeposited on the surface of the electric wire 12 by the electrodeposition coating method using the electrodeposition coating device 10 to form the insulating layer 21a. Specifically, a cylindrical electric wire 13 having a circular cross section, which is wound in a cylindrical shape, is electrically connected to the positive electrode of the DC power supply 14 via an anode 16. Then, the columnar electric wire 13 is pulled up in the direction of the solid arrow in FIG. 1 and undergoes the following steps.

First, as a first step, the columnar electric wire 13 is flatly rolled by a pair of rolling rollers 17 and 17 to form a flat electric wire 12 having a rectangular cross section. Examples of the electric wire include copper wire, aluminum wire, steel wire, copper alloy wire, aluminum alloy wire and the like. Next, as a second step, the electrodeposition liquid 11 is stored in the electrodeposition tank 18, preferably maintained at a temperature of 5 to 60 ° C., and is flat in the electrodeposition liquid 11 in the electrodeposition tank 18. Pass the electric wire 12. Here, a cathode 19 electrically connected to the negative electrode of the DC power supply 14 is inserted into the electrodeposition liquid 11 in the electrodeposition tank 18 at a distance from the passing flat electric wire 12. When the flat wire 12 passes through the electrodeposition liquid 11 in the electrodeposition tank 18, a DC voltage is applied between the flat wire 12 and the cathode 19 by the DC power supply 14. The DC voltage of the DC power supply 14 at this time is preferably 1 to 300 V, and the energization time of the DC current is preferably 0.01 to 30 seconds. As a result, in the electrodeposition liquid 11, negatively charged polymer particles (not shown) are electrodeposited on the surface of the flat wire 12 to form an insulating layer 21a.

Next, the flat electric wire 12 having the insulating layer 21a electrodeposited on the surface is subjected to a baking treatment to form an insulating film 21b on the surface of the electric wire 12. In this embodiment, the electric wire 12 having the insulating layer 21a formed on its surface is passed through the baking furnace 22. The baking treatment is preferably performed in a near-infrared heating furnace, a hot air heating furnace, an induction heating furnace, a far-infrared heating furnace, or the like. The temperature of the baking treatment is preferably in the range of 250 to 500 ° C., and the baking treatment time is preferably in the range of 1 to 10 minutes. The temperature of the baking process is the temperature of the central part in the baking furnace. By passing through the baking furnace 22, the insulated wire 23 in which the surface of the wire 12 is covered with the insulating film 21b is manufactured.

Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
3. 0.97 g of 1,3-dimethyl-2-imidazolidinone (DMI), diphenylmethane-4,4'-diisocyanate in a 2 liter four-necked flask equipped with a stirrer, a cooling tube, a nitrogen introduction tube and a thermometer. 508 g (30 mmol) and 5.764 g (30 mmol) of trimellitic anhydride were charged and the temperature was raised to 160 ° C. By reacting for about 6 hours, a polymer (polyamideimide resin) having a number average molecular weight of 40,000 was synthesized, and a polyamide-imide varnish (polyamideimide resin / DMI = 30 mass) having a polyamide-imide resin (nonvolatile content) concentration of 30% by mass was synthesized. % / 70% by mass) was obtained.

Next, 1.7 g of the obtained polyamide-imide varnish was further diluted with 4.8 g of DMI, 1.7 g of 1-methoxypropanol as a poor solvent and 0.02 g of tripropylamine as a basic compound were added, and then this solution was added. 1.8 g of water was added at room temperature (25 ° C.) while stirring at a high rotation speed of 10000 rpm. As a result, the electrodeposition liquid in which the polyamide-imide fine particles are dispersed (polyamide-imide resin / DMI / poor solvent / water / basic compound = 5% by mass / 60% by mass / 17% by mass / 18% by mass / 0.2% by mass). Got

<Examples 2 to 7 and Comparative Example 1>
As shown in Table 1 below, the electrodeposition solution was prepared in the same manner as in Example 1 except that the average particle size of the polymer particles, the type of the basic compound, and the ratio of each component in the electrodeposition solution were changed. Obtained. The average particle size of the polymer particles is a numerical value obtained by changing the ratio of other liquid components.

<Comparative tests and evaluations>
The electrodeposition solutions and the like obtained in Examples 1 to 7 and Comparative Example 1 were evaluated in the following (i) to (iii). These results are shown in Table 1 or Table 2 below.

(i) HSP distance to water: By substituting the HSP value of water and the HSP value of the nitrogen-containing compound used as the basic compound in each Example or Comparative Example into the following formula (1), each nitrogen The HSP distances of the contained compound and water were calculated respectively.

HSP distance = [4 × (dD _{1 −} dD ₂ ) ² + (dP _{1 −} dP ₂ ) ² + (dH _{1 −} dH ₂ ) ² ] ^1/2 (1)

(ii) Volume-based median diameter (D ₅₀ ): The polymer particles synthesized in each Example or Comparative Example were measured by a dynamic light scattering type particle size distribution measuring device (model name: LB-550 manufactured by HORIBA, Ltd.). The volume-based median diameter (D ₅₀ ) was measured.

(iii) Percentage of particles distributed within ± 30% of median diameter (D ₅₀ ): From the volume- based particle size distribution measured by the above device, within ± 30% of median diameter (D ₅₀ ) ([ D ₅₀ -0.3D _50] μm~ [was calculated percentage of D ₅₀ + 0.3D _50] the total number of particles of particles distributed in the range of [mu] m).

(iii) Storage stability: An insulating film was formed on the surface of the copper plate using the electrodeposition solution immediately after preparation obtained in each Example and Comparative Example and the electrodeposition solution stored for one month after adjustment. An insulator was prepared, and the storage stability of the electrodeposited liquid was evaluated by visually observing the presence or absence of air bubbles in the insulating film. In Table 2, "None" indicates that no air bubbles were confirmed in the insulating film. “Yes” indicates that one or more bubbles were confirmed in the insulating film.

The insulating material was produced by the procedure described later. Further, in each Example and Comparative Example, three insulating films having an insulating film thickness of 10 μm, 20 μm, and 30 μm were prepared for each electrodeposition liquid, respectively. The electrodeposition solution immediately after preparation refers to the electrodeposition solution before 24 hours have passed after preparation, and the electrodeposition solution stored for one month after adjustment means that the adjusted electrodeposition solution is sealed in a glass bottle. , An electrodeposition solution stored in the air at a temperature of 25 ° C. for one month. The film thickness is a value measured using a micrometer (model name: MDH-25M manufactured by Mitutoyo Co., Ltd.) after forming an insulating film on the surface of a copper plate.

Each insulation was prepared by the following procedure. First, the electrodeposition liquid was stored in the electrodeposition tank, and the temperature of the electrodeposition liquid in the electrodeposition tank was adjusted to 25 ° C. Next, an 18 mm square (thickness: 0.3 mm) copper plate and a stainless steel plate were prepared as anodes and cathodes, respectively, and placed in the electrodeposition liquid so as to face each other. Then, a DC voltage of 100 V was applied between the copper plate and the stainless steel plate to perform electrodeposition. At that time, the amount of electricity flowing by the Coulomb meter was confirmed, and when the amount of electricity reached a predetermined amount, the application of voltage was stopped. When forming an insulating film having a film thickness of 10 μm, the application of voltage is stopped when the amount of electricity reaches 0.05 C, and when forming an insulating film having a film thickness of 20 μm, the amount of electricity is 0. When the voltage reached 10 C, the voltage application was stopped, and when the insulating film having a film thickness of 30 μm was formed, the voltage application was stopped when the amount of electricity reached 0.15 C. As a result, an insulating layer was formed on the surface of the copper plate.

Next, a baking treatment was performed on a copper plate having an insulating layer formed on its surface. Specifically, the copper plate on which the insulating layer was formed was held in a baking oven maintained at a temperature of 250 ° C. for 3 minutes. As a result, an insulator having an insulating film formed on the surface of the copper plate was obtained. The temperature inside the baking furnace is the temperature at the center of the furnace measured by a thermocouple.

As is clear from Tables 1 and 2, when the electrodeposition solution immediately after preparation is used, the insulating films of Examples 1 to 7 and Comparative Example 1 are formed by foaming during drying or firing. No bubbles were found.

On the other hand, when comparing the insulating film formed by the electrodeposition solution stored for one month after preparation, in Comparative Example 1 in which a nitrogen-containing compound having an HSP distance of less than a predetermined value with water was used as the basic compound. , Bubbles were generated due to foaming during drying or firing in the insulating films of all thicknesses.

On the other hand, in Examples 1 to 7, when a nitrogen-containing compound having an HSP distance to water of a predetermined value or more was used as the basic compound, bubbles were formed in the 30 μm-thick insulating film of Examples 2 and 4 to 6. No bubbles due to foaming during drying or firing were observed in any of the insulating films, except that some of them were observed. From this, it was confirmed that the electrodeposition solutions of Examples 1 to 7 using a nitrogen-containing compound having an HSP distance of a predetermined value or more as a basic compound are extremely excellent in storage stability. In particular, in Examples 1 and 7, since the HSP distance to water as a basic compound is as large as 43.0 and 42.5, respectively, bubbles due to foaming during drying or firing are observed even if the film thickness is 30 μm. There wasn't.

INDUSTRIAL APPLICABILITY The present invention can be used for manufacturing power inductors for power supplies of personal computers, smartphones, etc., insulated electric wires used for transformers, reactors, motors, etc. of in-vehicle inverters, and other insulating materials.

11 Electrodeposition liquid

Claims (1)

In an electrodeposition solution for forming an aqueous dispersion type insulating film containing polymer particles, an organic solvent, a basic compound and water,
The polymer particles are polyamide-imides that do not have an anionic group in the main chain .
The basic compound is a nitrogen-containing compound having an HSP distance of 36.2 to 43.0 from water.
54 to 67% of all particles have a volume-based median diameter (D ₅₀ ) of 0.112 to 0.175 μm and are within ± 30% of the median diameter (D ₅₀ ) particle size of the polymer particles. (Volume standard )
An electrodeposition solution for forming an aqueous dispersion type insulating film, wherein the basic compound is an alkylamine compound.

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